Coating fluid for forming film, and film thereof and film-forming process

ABSTRACT

To provide a coating fluid for forming a film, which is curable sufficiently by heat treatment at a low temperature of at most 70° C. to form a cured film excellent in abrasion resistance and which is excellent in storage stability, a film obtained from the coating fluid for forming a film, and a process for forming the film. 
     A coating fluid for forming a film, which comprises a polysiloxane (A) obtained by condensation polymerization of a silicon compound of the formula (1) as the essential component, and a compound (B) of the formula (2):
 
Si(OR 1 ) 4   (1)
 
wherein R 1  is a C 1-5  hydrocarbon group,
 
                         
each of R 2 , R 3 , R 4  and R 5  which are independent of one another, is a hydrogen atom or a C 1-12  organic group.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coating field for forming a film,which contains, as the main component, a polysiloxane obtained bycondensation polymerization of an alkoxy group-containing siliconcompound, such as a coating fluid for forming a film, which is capableof forming a water repellent film, and a film formed from such a coatingfluid and a process for forming such a film.

2. Discussion of Background

Heretofore, it has been common to form a protective film on a substratesurface as a method for imparting an abrasion resistance to a plasticsubstrate made of an acrylic resin, a polyester or a polycarbonate.

As a coating fluid to form such a protective film, a heat curablecoating fluid containing, as the main component, a polysiloxane obtainedby hydrolytic condensation polymerization of a silicon compound such asa tetraalkoxysilane, has been developed. However, with such a heatcurable coating fluid, the heat treating temperature at the time offorming a film is restricted by e.g. the heat resistant temperature ofthe substrate, whereby there has been a case where the film is notsufficiently cured, and no adequate abrasion resistance can be obtained,and it has been desired to lower the heat treating temperature.

As a method for accomplishing such an object, for example, a method oflowering the temperature for forming a film has been proposed whichutilizes a catalytic reaction by adding a curing catalyst such as ametal salt of an organic acid, a tin alkyl ester compound, a tin halidecompound, a tin orthoester compound, a metal alcoholate, a titaniumchelate compound or a nitrogen-containing basic organic compound (PatentDocument 1), or a photocurable coating fluid requiring no heat treatmenthas been proposed which employs a photocurable resin compositioncomprising (A) an acrylate of bisphenol A diglycidyl ether polymer, (B)dipentaerythritol monohydroxy pentaacrylate, (C) a photopolymerizationinitiator, (D) inorganic particles and (E) a terminal reactivepolydimethylsiloxane (Patent Document 2).

In recent years, plastic substrates, particularly plastic films, tend tohave their thicknesses made thin for the purpose of high transparency,weight reduction, etc., and there has been a problem that they arelikely to be damaged by heat. A photocurable coating fluid has beendeveloped, but has been still inadequate. Accordingly, it has beendesired more than ever to develop a heat curable coating fluid forforming a film which is sufficiently curable by such a low temperaturetreatment that a plastic film will receive no damage.

On the other hand, it has been known that if a film showing a refractiveindex lower than the refractive index of a substrate is formed on thesurface of such a substrate, the reflectance of light reflecting fromthe surface of such a film will decrease. And, the film showing such adecreased light reflectance has been utilized as an antireflection filmand has been applied to various substrate surfaces.

A process for forming on a substrate an antireflection film showing alow refractive index, is disclosed wherein an alcohol dispersion of fineMgF₂ particles formed by reacting a magnesium salt or an alkoxymagnesiumcompound as a Mg source with a fluoride as a F source, or a liquidhaving a tetraalkoxysilane or the like added thereto for improvement ofthe film strength, is used as a coating fluid, and such a coating fluidis applied on a glass substrate such as a cathode ray tube and subjectedto heat treatment at from 100 to 500° C. (Patent Document 3).

A low reflection glass having formed on a glass substrate a thin filmshowing a refractive index of from 1.21 to 1.40, having micropits orconvexoconcaves with diameters of from 50 to 200 nm and having athickness of from 60 to 160 nm, is disclosed, wherein a coating fluid isprepared by mixing at least two types of hydrolytic condensationpolymers of tetraalkoxysilane, methyltrialkoxysilane,ethyltrialkoxysilane, etc. different in the average molecular weightwith a solvent such as an alcohol, a film is formed from such a coatingfluid by adjusting the mixing ratio in such mixing and by controllingthe relative humidity, and then the film is heated (Patent Document 4).

A low reflectance glass is disclosed which comprises a glass, anunderlayer film having a high refractive index formed on its surface,and an upper layer film having a low refractive index formed further onits surface (Patent Document 5). In this document, as a method forforming such an upper layer film, a method is disclosed wherein afluorinated silicon compound having a polyfluorocarbon chain such asCF₃(CF₂)₂C₂H₄Si(OCH₃)₃ and from 5 to 90 wt %, based thereon, of silanecoupling agent such as Si(OCH₃)₄ are hydrolyzed in an alcohol solvent inthe presence of a catalyst such as acetic acid at room temperature,followed by filtration to prepare a liquid of a co-condensate, and then,such a liquid is applied on the above-mentioned underlayer film andheated at from 120 to 250° C.

It is disclosed that a reaction mixture comprising a silicon compoundrepresented by Si(OR)₄, a silicon compound represented byCF₃(CF₂)_(n)CH₂CH₂Si(OR¹)₃, an alcohol represented by R²CH₂OH and oxalicacid in a specific ratio, is heated in the absence of water at from 40to 180° C. to form a polysiloxane solution, a coating fluid containingsuch a solution is applied on a substrate surface, and the applied filmis heat-cured at from 80 to 450° C. to form a film as adhered to thesubstrate surface, which has a refractive index of from 1.28 to 1.38 anda contact angle with water of from 90 to 115° (Patent Document 6).

In recent years, along with the progress in weight reduction orthickness reduction of display devices, an antireflection substrate,particularly an antireflection film, to be mounted thereon, is desiredto have the film thickness made thin for the purpose of weightreduction, high transparency or the like, whereby there has been aproblem that the film is susceptible to a damage by heat. Accordingly,it has been desired more than ever to develop a heat curable coatingfluid for forming a film, whereby an antireflection substrate can beobtained by such a low temperature treatment that the film is notsusceptible to a damage.

Patent Document 1: JP-A-07-082486

Patent Document 2: JP-A-11-124514

Patent Document 3: JP-A-05-105424

Patent Document 4: JP-A-06-157076

Patent Document 5: JP-A-61-010043

Patent Document 6: JP-A-09-208898

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a coating fluid forforming a film, which is sufficiently curable by heat treatment at atemperature of not higher than 70° C. to form a cured film excellent inabrasion resistance and which is excellent in storage stability, such asa coating fluid for forming a film which is capable of forming a waterrepellent film showing a low refractive index and being excellent inabrasion resistance, a film obtainable by such a coating fluid, such asa water repellent film, and a process for forming such a film.

Under the above-mentioned circumstances, the present inventors haveconducted an extensive study, and as a result, have accomplished thepresent invention. Namely, the present invention provides the following:

-   1. A coating fluid for forming a film, which comprises a    polysiloxane (A) obtained by condensation polymerization of a    silicon compound of the formula (1) as the essential component, and    a compound (B) of the formula (2):    Si(OR¹)₄  (1)    wherein R¹ is a C₁₋₅ hydrocarbon group,

each of R², R³, R⁴ and R⁵ which are independent of one another, is ahydrogen atom or a C₁₋₁₂ organic group.

-   2. The coating fluid for forming a film according to the above 1,    wherein the polysiloxane (A) is a polysiloxane obtained by    condensation polymerization of at least one silicon compound of the    formula (1) and at least one silicon compound of the formula (3):    (R⁶)_(n)Si(OR⁷)_(4-n)   (3)    wherein R⁶ is a hydrogen atom or a C₁₋₂₀ organic group, R⁷ is a C₁₋₅    hydrocarbon group, and n is an integer of from 1 to 3.-   3. The coating fluid for forming a film according to the above 2,    wherein the polysiloxane (A) is a polysiloxane obtained by    condensation polymerization in a ratio of from 0.02 to 0.80 mol of    the silicon compound of the formula (3) to 1 mol of the silicon    compound of the formula (1).-   4. The coating fluid for forming a film according to the above 1,    wherein the polysiloxane (A) is a polysiloxane obtained by    condensation polymerization of at least one silicon compound of the    formula (1) and at least one silicon compound of the formula (4):    (R^(2′))Si(OR^(3′))₃  (4)    wherein R^(2′) is a fluorinated C₁₋₂₀ organic group, and R^(3′) is a    C₁₋₅ hydrocarbon group.-   5. The coating fluid for forming a film according to the above 4,    wherein the polysiloxane (A) is a polysiloxane obtained by    condensation polymerization of at least one silicon compound of the    formula (1), at least one silicon compound of the formula (4) and at    least one silicon compound of the formula (5)    (R⁸)_(n)Si(OR⁹)_(4-n)  (5)    wherein R⁸ is a hydrogen atom or a C₁₋₂₀ organic group having no    fluorine, R⁹ is a C₁₋₅ hydrocarbon group, and n is an integer of    from 1 to 3.-   6. The coating fluid for forming a film according to the above 1,    which contains from 0.06 to 0.20 mol of the compound of the    formula (B) per mol of silicon atoms of the polysiloxane (A).-   7. The coating fluid for forming a film according to the above 1,    wherein the polysiloxane (A) is a polysiloxane obtained by    hydrolytic condensation polymerization of the silicon compound of    the formula (1) as the essential component.-   8. The coating fluid for forming a film according to the above 1,    wherein the polysiloxane (A) is a polysiloxane obtained by heating a    mixture of a silicon compound containing the silicon compound of the    formula (1) as the essential component, a solvent and oxalic acid.-   9. A film obtained by using the coating fluid for forming a film as    defined in the above 1.-   10. A cured film obtained by applying the coating fluid for forming    a film as defined in the above 1 on a substrate and curing it at a    temperature of from 40 to 70° C.-   11. A water repellent film obtained by applying the coating fluid    for forming a film as defined in the above 4 on a substrate and    curing it at a temperature of from 40 to 70° C.-   12. A water repellent film obtained by applying the coating fluid    for forming a film as defined in the above 5 on a substrate and    curing it at a temperature of from 40 to 70° C.-   13. An anti-reflection substrate having the water repellent film as    defined in the above 11.-   14. An anti-reflection substrate having the water repellent film as    defined in the above 12.-   15. An anti-reflection film having the water repellent film as    defined in the above 11.-   16. An anti-reflection film having the water repellent film as    defined in the above 12.-   17. A process for forming a film, which comprises applying the    coating fluid for forming a film as defined in the above 1 on a    substrate and curing it at a temperature of from 40 to 70° C.

The coating fluid for forming a film of the present invention isexcellent in storage stability and curable sufficiently by heattreatment at a low temperature at a level of from 40° C. to 70° C. andis capable of presenting a film excellent in abrasion resistance. And, afilm obtainable from the coating fluid of the present invention hasexcellent abrasion resistance as a protective film for e.g. a plasticfilm. Further, by the process for forming a film of the presentinvention, it is possible to form a film having such excellent abrasionresistance as mentioned above at a low temperature at a level of from40° C. to 70° C.

Further, in the coating fluid for forming a film of the presentinvention, the coating fluid for forming a water repellent filmemploying a specific polysiloxane, is excellent in storage stability andcurable sufficiently by heat treatment at a low temperature at a levelof from 40° C to 70° C. and is capable of providing a water repellentfilm showing a low refractive index and being excellent in abrasionresistance. And, the water repellent film obtainable from the coatingfluid for forming a water repellent film of the present invention can beused suitably for an antireflection substrate such as an antireflectionfilm. Further, by the process for forming a water repellent film of thepresent invention, it is possible to form a water repellent film havingsuch a low refractive index and excellent abrasion resistance asmentioned above at a low temperature at a level of from 40° C. to 70° C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, the present invention will be described in detail.

Polysiloxane (A)

The polysiloxane (A) to be used in the present invention, is obtained bycondensation polymerization of a silicon compound of the formula (1) asthe essential component:Si(OR¹)₄  (1)wherein R¹ is a C₁₋₅ hydrocarbon group.

Namely, it is a polysiloxane obtained by condensation polymerization ofa tetraalkoxysilane as the essential component.

In the formula (1), R¹ is a hydrocarbon group. The smaller the carbonnumber, the higher the reactivity. Accordingly, it is preferably a C₁₋₅saturated hydrocarbon group. It is more preferably a methyl group, anethyl group, a propyl group or a butyl group. Specific examples of sucha tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane,tetrapropoxysilane and tetrabutoxysilane, and they are readilycommercially available.

In the present invention, at least one type among silicon compounds ofthe formula (1) may be employed, but a plurality of different types maybe employed, as the case requires.

Further, the polysiloxane (A) may be one obtained by condensationpolymerization of a silicon compound of the formula (1) and a siliconcompound of the formula (3):(R⁶)_(n)Si(OR⁷)_(4-n)  (3)wherein R⁶ is a hydrogen atom or a C₁₋₂₀ organic group, R⁷ is ahydrocarbon group, and n is an integer of from 1 to 3.

The silicon compound of the formula (3) is an alkoxysilane having 1, 2or 3 alkoxy groups and R⁷ is a hydrocarbon group. Namely, in a casewhere n is 1 or 2, the plurality of R⁷ are usually the same in manycases. However, in the present invention, the plurality of R⁷ may be thesame or different.

Specific examples of such a silicon compound of the formula (3) will beshown below.

Namely, a trialkoxysilane such as methyltrimethoxysilane,methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane,propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane,butyltriethoxysilane, pentyltrimethoxysilane, pentyltriethoxysilane,hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane,heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane,dodecyltrimethoxysilane, dodecyltriethoxysilane,hexadecyltrimethoxysilane, hexadecyltriethoxysilane,octadecyltrimethoxysilane, octadecyltriethoxysilane,phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane,vinyltriethoxysilane, γ-aminopropyltrimethoxysilane,γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane,γ-methacryloxypropyltriethoxysilane, trifluoropropyltrimethoxysilane,trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane,tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilaneor heptadecafluorodecyltriethoxysilane, a dialkoxysilane such asdimethyldimethoxysilane or dimethyldiethoxysilane, and atrialkylalkoxysilane such as trimethylmethoxysilane ortrimethylethoxysilane, may, for example, be mentioned.

With such a silicon compound, the smaller the carbon number of R⁷, thehigher the reactivity. Accordingly, a carbon number of from 1 to 5 ispreferred. More preferred is a carbon number of from 1 to 3.

In the present invention, at least one type selected from siliconcompounds of the formula (3) may be employed, but a plurality ofdifferent types may be employed as the case requires.

Further, in the present invention, the amount of the silicon compound ofthe formula (3) to be used in combination with the silicon compound ofthe formula (1) is not particularly limited, but it is preferably from0.02 to 0.80 mol per mol of the silicon compound of the formula (1).Further, the polysiloxane (A) may be one obtained by copolymerization ofa silicon compound of the formula (1) and a silicon compound of theformula (4). (Hereinafter a coating fluid for forming a film containingsuch a polysiloxane (A) will be referred to also as “a coating fluid forforming a water repellent film”.)(R^(2′))Si(OR^(3′))₃  (4)wherein R_(2′) is a fluorinated C₁₋₁₄ organic group, and R^(3′) is aC₁₋₅ hydrocarbon group.

The silicon compound of the formula (4) is one to impart waterrepellency to the film. Here, R^(2′) in the formula (4) is a fluorinatedC₁₋₁₅ organic group. The number of fluorine atoms in this organic groupis not particularly limited. Further, R^(3′) in the formula (4) is aC₁₋₅ hydrocarbon group, preferably a C₁₋₅ saturated hydrocarbon group,more preferably a methyl group, an ethyl group, a propyl group or abutyl group.

Among such silicon compounds of the formula (4), a silicon compound ofthe formula (4′) is preferred.CF₃(CF₂)_(m)CH₂CH₂Si(OR¹⁰)₃  (4′)wherein m is an integer of from 0 to 12, and R¹⁰ is a C₁₋₅ hydrocarbongroup.

R¹⁰ in the formula (4′) is a C₁₋₅ hydrocarbon group, and like the aboveR^(3′), it is preferably a C₁₋₅ saturated hydrocarbon group, morepreferably a methyl group, an ethyl group, a propyl group or a butylgroup.

Specific examples of such a silicon compound of the formula (4′) includetrifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane,tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane,heptadecafluorodecyltrimethoxysilane andheptadecafluorodecyltriethoxysilane.

In the coating fluid for forming a water repellent film of the presentinvention, at least one type selected from silicon compounds of theformula (4) may be employed, but a plurality of different types may beemployed, as the case requires.

The polysiloxane (A) to be used for the coating fluid for forming awater repellent film of the present invention can be obtained bycondensation polymerization of silicon compounds of the formulae (1) and(4), and the ratio of condensation polymerization of the siliconcompounds of the formulae (1) and (4) is not particularly limited solong as the polysiloxane is in a homogeneous solution state in thesolvent. If the ratio of the silicon compound of the formula (4) is atleast 0.05 mol per mol of the silicon compound of the formula (1), awater repellent film having a contact angle with water of at least 90°tends to be easily obtainable, such being desirable. If it is at most0.43 mol, a homogeneous polysiloxane (A) solution tends to be readilyobtainable, such being preferred.

Further, the polysiloxane (A) may be one obtained by condensationpolymerization of the silicon compounds of the formulae (1) and (4) anda silicon compound of the formula (5):(R⁸)_(n)Si(OR⁹)_(4-n)  (5)wherein R⁸ is a hydrogen atom or a C₁₋₂₀ organic group having nofluorine, R⁹ is a C₁₋₅ hydrocarbon group, and n is an integer of from 1to 3.

The silicon compound of the formula (5) is an alkoxysilane having ahydrogen atom or a C₁₋₂₀ organic group having no fluorine, and 1, 2 or 3alkoxy groups. R⁹ in the formula (5) is a hydrocarbon group. Namely,when n is 1 or 2, the plurality of R⁹ may be the same in many cases.However, in the present invention, the plurality of R⁹ may be the sameor different. Specific examples of such a silicon compound of theformula (5) will be shown below.

A trialkoxysilane such as methyltrimethoxysilane, methyltriethoxysilane,ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane,propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane,pentyltrimethoxysilane, pentyltriethoxysilane, hexyltrimethoxysilane,hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane,octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane,dodecyltriethoxysilane, hexadecyltrimethoxysilane,hexadecyltriethoxysilane, octadecyltrimethoxysilane,octadecyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane,vinyltrimethoxysilane, vinyltriethoxysilane,γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-methacryloxypropyltrimethoxysilane orγ-methacryloxypropyltriethoxysilane, a dialkoxysilane such asdimethyldimethoxysilane or dimethyldiethoxysilane, and atrialkylalkoxysilane such as trimethylmethoxysilane ortrimethylethoxysilane.

In such a silicon compound, R⁹ is a C₁₋₅ hydrocarbon group, preferably aC₁₋₅ saturated hydrocarbon group, more preferably a C₁₋₃ saturatedhydrocarbon group.

In the present invention, a plurality of silicon compounds of theformula (5) may be used as the case requires.

Further, in the present invention, the amount of the silicon compound ofthe formula (5) to be combined with the silicon compounds of theformulae (1) and (4) is not particularly limited. However, it ispreferably from 0.02 to 0.80 mol per mol of the total amount of siliconatoms in the silicon compounds of the formulae (1) and (4).

The polysiloxane (A) to be used in the present invention is notparticularly limited so long as it is a condensation polymer of asilicon compound of the formula (1), or silicon compounds of theformulae (1) and (3) or silicon compounds of the formulae (1) and (4),or silicon compounds of the formulae (1), (4) and (5).

The polysiloxane (A) to be used in the present invention can usually beobtained by hydrolysis and condensation polymerization by a knownmethod. The most widely known method is a hydrolysis method wherein purewater or a mixed solution of pure water and a solvent is added by such amethod as dropwise addition to a solution having a silicon compound orsilicon compounds dissolved in a solvent, followed by heating andstirring at a temperature of at least 40° C. for at least a few hours.In this method, the amount of pure water to be used is optionallysuitably selected depending upon the purpose of complete hydrolysis orpartial hydrolysis. Usually, it is from 0.4 to 4 mol per mol of thetotal alkoxy groups of the silicon compounds. In the present invention,either the total hydrolysis or partial hydrolysis may be employed. And,in this hydrolysis method, in order to accelerate the hydrolysis andcondensation polymerization reaction, an acid or an alkali may usuallybe added as a catalyst. As such an acid catalyst, an inorganic acid suchas hydrochloric acid or sulfuric acid, or an organic acid such as oxalicacid or formic acid may be mentioned. As an alkali catalyst, aninorganic alkali such as sodium, potassium or ammonia, or various aminesmay be employed. The heating temperature and heating time may beselected suitably as the case requires. For example, a method of heatingand stirring at 50° C. for 24 hours or heating and stirring under refluxfor 8 hours, may be mentioned. Further, so long as silicon compoundsundergo hydrolysis and condensation polymerization, it is possible touse a method of stirring at room temperature without heating.

Further, another method for obtaining the polysiloxane (A) may, forexample, be a method of heating a mixture of a silicon compound orsilicon compounds, a solvent and oxalic acid. Specifically, an alcoholis added to oxalic acid to preliminarily obtain an alcohol solution ofoxalic acid, and then such a solution is mixed with a silicon compoundor silicon compounds, followed by heating. At that time, the amount ofoxalic acid is usually from 0.2 to 2 mol per mol of total alkoxy groupsin the silicon compound or silicon compounds. The heating in this methodmay be carried out at a liquid temperature of from 50 to 180° C. Forexample, it is carried out under reflux for from a few tens minutes toabout ten hours.

In any one of the above methods, it is usual to carry out condensationpolymerization of silicon compounds at a SiO₂ solid contentconcentration of the charged silicon compounds of at most 20 mass %. Byselecting an optional concentration within such concentration range, itis possible to suppress formation of a gel and to obtain a homogeneouspolysiloxane-containing solution.

The solvent to be used in the above process is not particularly limitedso long as it is capable of dissolving silicon compounds of the formulae(1) and (3), or the formulae (1) and (4), or the formulae (1), (4) and(5). Usually, as an alcohol will be formed by the condensationpolymerization reaction of silicon compounds, an alcohol or an organicsolvent having good compatibility with an alcohol, may be employed.Specific examples of such an organic solvent include methanol, ethanol,propanol, n-butanol, ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, diethylene glycol monomethyl ether and diethyleneglycol monoethyl ether.

In the present invention, the above organic solvents may be used incombination as a mixture of two or more of them.

Compound (B)

The compound (B) to be used in the present invention is an urea of theformula (2) or its derivative.

wherein each of R², R³, R⁴ and R⁵ which are independent of one another,is a hydrogen atom or a C₁₋₁₂ organic group.

The compound (B) is considered to be decomposed by heating or hydrolysiswith moisture in the atmosphere to accelerate condensation of alkoxygroups remaining in the coated film thereby to promote curing of thecoated film, and accordingly, it is preferably a compound readilydecomposable at a low temperature.

Accordingly, each of R², R³, R⁴ and R⁵ in the formula (2) which areindependent of one another, is a hydrogen atom or a C₁₋₁₂ organic group,and preferably, each of R², R³, R⁴ and R⁵ which are independent of oneanother, is a hydrogen atom or a C₁₋₅ organic group.

Specific examples of such a urea or its derivative include urea,1,1-dimethylurea, 1,1-diethylurea, 1,3-dimethylurea, 1,3-diethylurea,tetramethylurea, tetraethylurea, hydroxyethylurea, hydroxypropylurea,ethylurea and propylurea.

The content of such a compound (B) is preferably at least 0.06 mol permol of silicon atoms in the polysiloxane (A), to facilitate curing at alow temperature. Further, the content of the compound (B) is preferablyat most 0.20 mol, whereby the water repellent film will be transparentand free from irregularity, and a high film hardness can easily beobtained.

Other Components

In the present invention, in addition to the polysiloxane solution (A)and the compound (B), other components such as inorganic fine particles,a leveling agent and a surfactant may, for example, be incorporated.

As the inorganic fine particles, fine particles such as silica fineparticles, alumina fine particles, titania fine particles and magnesiumfluoride fine particles are preferred, and ones in the form of acolloidal solution are particularly preferred. Such a colloidal solutionmay be one having inorganic fine particles dispersed in a dispersionmedium, or it may be a commercially available colloidal solution. In thepresent invention, by incorporating inorganic fine particles, it becomespossible to impart the surface shape or other functions to the curedfilm to be formed. As such inorganic fine particles, the averageparticle diameter is preferably from 0.001 to 0.2 μm, more preferablyfrom 0.001 to 0.1 μm. If the average particle diameter of the inorganicfine particles exceeds 0.2 μm, the transparency of a cured film formedby a coating fluid thus prepared is likely to be low.

As the dispersion medium for the inorganic fine particles, water or anorganic solvent may be mentioned. As a colloidal solution, from theviewpoint of the stability of the coating fluid for forming a film, thepH or pKa is preferably adjusted to be from 2 to 10, more preferablyfrom 3 to 7.

The organic solvent to be used as a dispersion medium for the colloidalsolution may, for example, be an alcohol such as methanol, isopropylalcohol, ethylene glycol, butanol or ethylene glycol monopropyl ether, aketone such as methyl ethyl ketone or methyl isobutyl ketone, an organichydrocarbon such as toluene or xylene, an amide such asdimethylformamide, dimethylacetamide or N-methylpyrrolidone, an estersuch as ethyl acetate, butyl acetate or γ-butyrolactone, or an ethersuch as tetrahydrofuran or 1,4-dioxane. Among them, an alcohol or aketone is preferred. These organic solvents may be used alone or incombination as a mixture of two or more of them as a dispersion medium.

Further, the leveling agent and the surfactant may be conventional ones,and commercial products are preferred, since they are readily available.

Coating Fluid for Forming a Film

The method for preparing the coating fluid for forming a film of thepresent invention is not particularly limited, so long as thepolysiloxane (A) and the compound (B) are uniformly mixed. Usually, thepolysiloxane (A) is obtained in a state of a solution by condensationpolymerization of a silicon compound or silicon compounds in a solvent.Therefore, a method wherein a solution of the polysiloxane (A) obtainedby condensation polymerization of a silicon compound or siliconcompounds (hereinafter referred to as a polysiloxane (A) solution) ismixed as it is with the compound (B), is preferred. Otherwise, as thecase requires, the polysiloxane (A) solution may be concentrated ordiluted by an addition of a solvent, or the solvent may be substitutedby another solvent, and then mixed with the compound (B). Further, thepolysiloxane (A) solution and the compound (B) may be mixed and then thesolvent may be added.

The SiO₂ solid content concentration in the coating fluid for forming afilm at that time is preferably from 0.5 to 15 mass %. If the SiO₂concentration is lower than 0.5 mass %, it tends to be difficult toobtain a desired film thickness by one coating operation, and if it ishigher than 15 mass %, the pot life of the solution is likely to beinadequate.

The solvent to be used for dilution or substitution may be the samesolvent as used for the condensation polymerization of the siliconcompounds or may be another solvent. Such a solvent is not particularlylimited so long as it does not impair the compatibility with thepolysiloxane (A) and the compound (B), and one solvent or a plurality ofsolvents may optionally be selected for use.

Specific examples of such a solvent include an alcohol such as methanol,ethanol, isopropanol, butanol or diacetone alcohol, a ketone such asacetone, methyl ethyl ketone or methyl isobutyl ketone, a glycol such asethylene glycol, propylene glycol or hexylene glycol, a glycol ethersuch as methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethylcarbitol, butyl carbitol, diethylene glycol monomethyl ether, propyleneglycol monomethyl ether or propylene glycol monobutyl ether, and anester such as methyl acetate, ethyl acetate or ethyl lactate.

The method for mixing the above-mentioned other components is notparticularly limited, and they may be mixed at the same time as thepolysiloxane (A) and the compound (B) or after mixing the polysiloxane(A) and the compound (B).

Specific examples of the coating fluid for forming a film in the presentinvention will be mentioned below.

-   (1) A coating fluid for forming a film comprising the    polysiloxane (A) and the compound (B).-   (2) The coating fluid for forming a film comprising the above (1)    and inorganic fine particles.-   (3) The coating fluid for forming a film comprising the above (1) or    (2), and at least one member selected from the group consisting of a    leveling agent and a surfactant.    Formation of a Film

The coating fluid for forming a film of the present invention is appliedto a substrate, followed by heat curing to obtain a desired film. As thecoating method, a known or well known method may be employed. Forexample, a method such as a dipping method, a flow coating method, aspraying method, a bar coating method, a gravure coating method, a rollcoating method, a blade coating method or an air knife coating methodmay be employed. At that time, the substrate to be used may be asubstrate made of e.g. plastic, glass or ceramics. As a plasticsubstrate, a plate or film of e.g. polycarbonate, poly(meth)acrylate,polyether sulfone, polyarylate, polyurethane, polysulfone, polyether,polyether ketone, trimethylpentene, polyolefin, polyethyleneterephthalate, (meth)acrylonitrile, triacetyl cellulose, diacetylcellulose or acetate butyrate cellulose may, for example, be mentioned.

The film formed on the substrate may be heat-cured as it is at atemperature of from 40 to 70° C. However, it may be dried beforehand ata temperature of from room temperature to 100° C. and then heat-cured.In such a case, the time required for drying is preferably from 10seconds to 6 minutes.

The time required for heat curing may suitably be selected dependingupon the desired film characteristics. However, it is usually from 1hour to 7 days. When a low curing temperature is selected, the curingtime may be prolonged to obtain a cured film having sufficient abrasionresistance.

Further, the coating fluid for forming a film of the present inventionis capable of obtaining a film excellent in abrasion resistance even ata curing temperature exceeding 70° C.

A water repellent film of the present invention obtained by the abovemethod using a coating fluid for forming a water repellent film hascharacteristics such that the contact angle with water is at least 90°,the refractive index is low at a level of at most 1.4 and it isexcellent in abrasion resistance. Accordingly, it is particularly usefulfor antireflection purposes.

In a case where the water repellent film of the present invention is tobe used for the antireflection purposes, the water repellent film of thepresent invention is formed on a substrate having a refractive indexhigher than the refractive index of the water repellent film of thepresent invention, e.g. on the surface of usual glass, whereby it isreadily possible to convert such a substrate to a substrate having anantireflection ability. The water repellent film of the presentinvention is effective when it is used as a single film on the substratesurface, but it may also be effectively used for an antireflectivemultilayered body having the film formed on an underlayer film having ahigh refractive index.

With respect to the relation between the thickness of a film and thewavelength of light, it is known that between the thickness d (nm) of afilm having a refractive index a and the wavelength λ (nm) of lightdesired to have the reflectance reduced by the film, a relation ofd=(2b−1)λ/4a (wherein b is an integer of at least 1) is satisfied.Accordingly, by setting the thickness of the film by using this formula,it is readily possible to prevent reflection of light with the desiredwavelength. In a specific example, in a case where with respect to lightwith a wavelength of 550 nm, in order to prevent reflection of lightfrom a glass surface by forming a film having a refractive index of1.32, such numerical values may be substituted for λ and a in the aboveformula to obtain the optimum film thickness. At that time, an optionalpositive integer may be substituted for b. For example, the filmthickness obtained by substituting 4 for b is 104 nm, and the filmthickness obtained by substituting 2 for b is 312 nm. By adopting thefilm thickness thus calculated, it is readily possible to impart anantireflection ability.

The thickness of the film to be formed on a substrate may be adjusted bythe film thickness during the coating, but it may easily be adjusted byadjusting the SiO₂ concentration in the coating fluid.

A water repellent film of the present invention is useful in a fieldwhere antireflection of light is desired, such as a cathode ray tubemade of glass, a display of a computer, a mirror having a glass surfaceor a showcase made of glass. Further, the water repellent film of thepresent invention has sufficient practical efficiency from the viewpointof an antifouling property in that a fingerprint or oil-based ink caneasily be wiped off, and it can sufficiently be cured by low temperaturetreatment at a level of from 40 to 70° C., whereby it is usefulparticularly for an antireflection film for a liquid crystal TV or adisplay monitor.

Now, the present invention will be described in further detail withreference to Preparation Examples, Working Examples and ComparativeExamples. However, it should be understood that the present invention isby no means restricted by the following Examples.

Abbreviations in the Examples are as follows.

TEOS: Tetraethoxysilane

MTES: Methyltriethoxysilane

HTES: Hexyltriethoxysilane

MPS: γ-Mercaptopropyltrimethoxysilane

MAPS: γ-Methacryloxypropyltrimethoxysilane

GPS: γ-Glycidoxypropyltrimethoxysilane

FS-03: 3,3,3-Trifluoropropyltrimethoxysilane

FS-13: Tridecafluorooctyltrimethoxysilane

FS-17: Heptadecafluorododecyltrimethoxysilane

1,1-DMU: 1,1-Dimethylurea

1,3-DMU: 1,3-Dimethylurea

TMU: Tetramethylurea

HEU: Hydroxyethylurea

BCS: Butyl cellosolve

The measuring methods used in the following Preparation Examples are asfollows.

Method for Measuring Residual Alkoxysilane Monomer

The alkoxysilane monomer remaining in the solution of the polysiloxane(A) was measured by gas chromatography (hereinafter referred to as GC).

The GC measurement was carried out under the following conditions byusing Shimadzu GC-14B, manufactured by Shimadzu Corporation.

Column: Capillary column CBPI-W25-100 (25 mm×0.53 mmΦ×1 μM)

Column temperature: It was raised at a rate of 15° C./min from theinitial temperature of 50° C. to the final temperature of 290° C. (3minutes).

Amount of sample injected: 1 μL, injection temperature: 240° C.,detector temperature: 290° C., carrier gas: nitrogen (flow rate: 30mL/min), detection method: FID method.

PREPARATION EXAMPLE 1

Into a four-necked reaction flask equipped with a reflux condenser,61.16 g of ethanol was put, and 18.01 g of oxalic acid was graduallyadded with stirring to obtain an ethanol solution of oxalic acid. Then,this solution was heated, and 20.83 g of TEOS was dropwise added underreflux. After the dropwise addition, refluxing was carried out for 5hours, followed by cooling naturally to room temperature to obtain apolysiloxane (A) solution (P1). This polysiloxane (A) solution (P1) wasmeasured by GC, whereby no alkoxysilane monomer was detected.

PREPARATION EXAMPLES 2 TO 4

With compositions shown in Table I-1, polysiloxane (A) solutions (P2 toP4) were obtained in the same manner as in Preparation Example 1. Atthat time, instead of TEOS in Preparation Example 1, a monomer mixturehaving a plurality of silicon compounds (hereinafter referred to asmonomers) preliminarily mixed, was used.

The obtained polysiloxane (A) solutions (P2 to P4) were respectivelymeasured by GC, whereby no alkoxysilane monomer was detected.

TABLE I-1 Oxalic Polysiloxane Silicon acid Ethanol (A) solution compound(g) (g) (g) Preparation P1 TEOS 18.01 61.16 Example 1 20.83 (0.10 mol)Preparation P2 TEOS MTES 18.01 61.45 Example 2 18.75 8.92 (0.09 mol)(0.01 mol) Preparation P3 TEOS HTES 18.01 61.17 Example 3 18.75 2.07(0.09 mol) (0.01 mol) Preparation P4 TEOS MAPS 18.01 60.76 Example 418.75 2.48 (0.09 mol) (0.01 mol)

PREPARATION EXAMPLE 5

Into a four-necked reaction flask equipped with a reflux condenser,50.11 g of ethanol was put, and 34.73 g of TEOS was added with stirring.Then, a solution having 0.15 g of oxalic acid dissolved in 15.01 g ofwater was gradually dropwise added. Thereafter, the mixture was heated,refluxed for 1 hour and then left to cool to room temperature to obtaina polysiloxane (A) solution (P5). This polysiloxane (A) solution (P5)was measured by GC, whereby no alkoxysilane monomer was detected.

PREPARATION EXAMPLE 6

Into a four-necked reaction flask equipped with a reflux condenser,50.31 g of ethanol was put, and 31.26 g of TEOS and 3.27 g of MPS wereadded with stirring. Then, a solution having 0.15 g of oxalic aciddissolved in 15.01 g of water was gradually dropwise added. Thereafter,the mixture was heated, refluxed for 1 hour and then left to cool toroom temperature to obtain a polysiloxane (A) solution (P6). Thispolysiloxane (A) solution (P6) was measured by GC, whereby noalkoxysilane monomer was detected.

PREPARATION EXAMPLE 7

Into a 300 ml eggplant type flask, 48.59 g of ethanol was put, and 34.68g of TEOS was added with stirring. Then, a diluted solution having 1.74g of a 60% nitric acid aqueous solution added to 14.99 g of water, wasgradually dropwise added. Thereafter, the mixture was stirred at roomtemperature for 1 hour to obtain a polysiloxane (A) solution (P7). Thispolysiloxane (A) solution (P7) was measured by GC, whereby noalkoxysilane monomer was detected.

EXAMPLES 1 TO 11 AND COMPARATIVE EXAMPLES 1 TO 3

With the compositions shown in Table I-2, the polysiloxane (A) solution,the compound (B), BCS and ethanol were mixed to obtain coating fluids(Q1 to Q11).

Further, in Comparative Examples, with the compositions shown in TableI-2, the polysiloxane (A) solution, BCS and ethanol were mixed to obtaincoating fluids (T1 to T3).

TABLE I-2 Poly- Molar siloxane ratio of (A) Si/ Coating solutionCompound BCS Ethanol Compound fluid (g) (B) (g) (g) (g) (b) Ex. 1 Q1 P1Urea 10.00 56.56 100/6  33.33 0.12 Ex. 2 Q2 P1 1,1-DMU 10.00 56.32100/12 33.33 0.35 Ex. 3 Q3 P1 1,3-DMU 10.00 56.50 100/6  33.33 0.17 Ex.4 Q4 P1 TMU 10.00 56.21 100/12 33.33 0.46 Ex. 5 Q5 P1 HEU 10.00 56.46100/6  33.33 0.21 Ex. 6 Q6 P2 Urea 10.00 56.43 100/12 33.33 0.24 Ex. 7Q7 P3 Urea 10.00 56.43 100/12 33.33 0.24 Ex. 8 Q8 P4 Urea 10.00 56.43100/12 33.33 0.24 Ex. 9 Q9 P5 Urea 10.00 69.76 100/12 20 0.24 Ex. 10 Q10P6 Urea 10.00 69.76 100/12 20.00 0.24 Ex. 11 Q11 P7 Urea 10.00 69.88100/6  20.00 0.12 Comp. T1 P1 — 10.00 56.67 — Ex. 1 33.33 Comp. T2 P6 —10.00 70.00 — Ex. 2 20.00 Comp. T3 P7 — 10.00 70.00 — Ex. 3 20.00

The storage stability of the prepared coating fluids (Q1 to Q11 and T1to T3) was evaluated by the following method. The results are shown inTable I-3.

Storage Stability

Each coating fluid was left to stand still at room temperature for 1month, and then 100 cc thereof was subjected to filtration by means of anon-aqueous type polytetrafluoroethylene filter having a pore diameterof 0.45 μm and Φ×L being 18×22 mm (Chromatodisk 13N, manufactured byKurabo Industries Ltd.), whereby one which was filterable was identifiedby ◯, and one which led to clogging was identified by ×.

Further, each coating fluid (Q1 to Q11 and T1 to T3) was applied on asilica-coated glass substrate by means of a bar coater (No. 9) to form acoated film. It was left to stand at room temperature for 30 seconds andthen dried in a clean oven at 100° C. for 5 minutes to form a cured filmunder the condition as identified in Table I-3. With respect to theobtained cured film, the adhesion and abrasion resistance were evaluatedby the following methods. The evaluation methods are as follows, and theevaluation results are shown in Table I-3.

Adhesion

Each cured film on the substrate was cross-cut at 1 mm intervals to form100 sections, and an adhesive tape (Cellotape, registered trademark,manufactured by Nichiban Co., Ltd., 24 mm in width) was firmly bonded tothe cured film, and then, the adhesive tape was quickly peeled wherebypresence or absence of peeling of the cured film was visually confirmed.One having no peeling was identified by ◯, and one having peelingobserved was identified by ×.

Abrasion Resistance

By means of steel wool #0000 manufactured by Nippon Steel Wool, eachcured film was rubbed 10 reciprocations under a load of 300 g/cm². andscratching on the cured film surface was visually evaluated. Theevaluation standards were as follows.

A: 0 to 5 scratch marks, B: 6 to 10 scratch marks, C: 11 to 20 scratchmarks, D: 21 or more scratch marks

TABLE I-3 Curing Coating conditions Storage Abrasion fluid Temp. Timestability Adhesion resistance Ex. 1 Q1 40° C. 3 days ◯ ◯ A Ex. 2 Q2 40°C. 3 days ◯ ◯ A Ex. 3 Q3 40° C. 3 days ◯ ◯ A Ex. 4 Q4 40° C. 3 days ◯ ◯A Ex. 5 Q5 40° C. 3 days ◯ ◯ A Ex. 6 Q6 40° C. 3 days ◯ ◯ A Ex. 7 Q7 40°C. 3 days ◯ ◯ A Ex. 8 Q8 40° C. 3 days ◯ ◯ A Ex. 9 Q9 40° C. 3 days ◯ ◯B Ex. 10 Q10 40° C. 4 hours ◯ ◯ A Ex. 11 Q11 40° C. 2 hours ◯ ◯ A Comp.T1 40° C. 3 days ◯ ◯ D Ex. 1 Comp. T2 40° C. 4 hours ◯ ◯ D Ex. 2 Comp.T3 40° C. 2 hours ◯ ◯ D Ex. 3

Examples 1 to 11 were excellent in storage stability and adhesion, andthe abrasion resistance was excellent at a level of at least B.

In Comparative Examples 1 to 3 containing no compound (B), the abrasionresistance was D, and many scratch marks were observed on the filmsurface.

REFERENCE EXAMPLE 1

The prepared coating fluid Q1 was applied on a silica-coated glasssubstrate by means of a bar coater (No. 9) to form a film. It was leftto stand at room temperature for 30 seconds and then dried in a cleanoven at 100° C. for 5 minutes. Thereafter, no heat treatment for curingwas carried out. With respect to this film, the adhesion and abrasionresistance were evaluated in the same manner as in the above Examples,whereby the adhesion was ◯, and the abrasion resistance was D.

Now, Examples relating to coating fluids for forming water repellentfilms will be described.

PREPARATION EXAMPLE 21

Into a four-necked reaction flask equipped with a reflux condenser,58.56 g of methanol was put, and 18.01 g of oxalic acid was graduallyadded with stirring to prepare an ethanol solution of oxalic acid. Then,this solution was heated and a mixture of TEOS (18.75 g) and FS-13 (4.68g) was dropwise added under reflux. After the dropwise addition, themixture was refluxed for 5 hours and left to cool to room temperature toobtain a polysiloxane (A) solution (P21). This polysiloxane (A) solution(P21) was measured by GC, whereby no alkoxysilane monomer was detected.

PREPARATION EXAMPLES 22 TO 27

With the compositions shown in Table II-1, polysiloxane (A) solutions(P22 to P27) were obtained in the same manner as in Preparation Example21. At that time, a plurality of silicon compounds (hereinafter referredto as monomers) were preliminarily mixed for use.

The obtained polysiloxane (A) solutions (P22 to P27) were respectivelymeasured by GC, whereby no alkoxysilane monomer was detected.

TABLE II-1 Polysiloxane Oxalic (A) acid Methanol solution Siliconcompounds (g) (g) (g) Prep. P21 TEOS FS-13 — 18.01 58.56 Ex. 21 18.754.68 0.0900 mol 0.0100 mol Prep. P22 TEOS FS-13 — 18.01 57.91 Ex. 2218.23 5.85 0.0875 mol 0.0125 mol Prep. P23 TEOS FS-13 — 18.01 57.26 Ex.23 17.71 7.02 0.0850 mol 0.0150 mol Prep. P24 TEOS FS-13 — 18.01 56.61Ex. 24 17.19 8.19 0.0825 mol 0.0175 mol Prep. P25 TEOS FS-13 GPS 18.0158.42 Ex. 25 17.71 4.68 1.18 0.0850 mol 0.0100 mol 0.0050 mol Prep. P26TEOS FS-03 18.01 61.01 Ex. 26 17.71 3.27 0.0850 mol 0.0150 mol Prep. P27TEOS FS-17 18.01 59.36 Ex. 27 19.79 2.84 0.0950 mol 0.0050 mol

EXAMPLES 21 TO 31, AND COMPARATIVE EXAMPLES 21 to 27

With the compositions shown in Table II-2, the polysiloxane (A)solution, the compound (B), BCS and methanol were mixed to obtaincoating fluids (Q21 to Q31).

Further, in Comparative Examples, with the compositions shown in TableII-2, the polysiloxane (A) solution, BCS and methanol were mixed toobtain coating fluids (T21 to T27).

TABLE II-2 Poly- Molar siloxane ratio of (A) Com- Si/ Coating solutionpound BCS Methanol Compound fluid (g) (B) (g) (g) (g) (b) Ex. 21 Q21 P21Urea 10.00 56.43 100/12 33.33 0.24 Ex. 22 Q22 P22 Urea 10.00 56.43100/12 33.33 0.24 Ex. 23 Q23 P23 Urea 10.00 56.43 100/12 33.33 0.24 Ex.24 Q24 P24 Urea 10.00 56.43 100/12 33.33 0.24 Ex. 25 Q25 P25 Urea 10.0056.43 100/12 33.33 0.24 Ex. 26 Q26 P23 1,1-DMU 10.00 56.32 100/12 33.330.35 Ex. 27 Q27 P23 1,3-DMU 10.00 56.32 100/12 33.33 0.35 Ex. 28 Q28 P23TMU 10.00 56.21 100/12 33.33 0.46 Ex. 29 Q29 P23 HEU 10.00 56.25 100/1233.33 0.42 Ex. 30 Q30 P26 Urea 10.00 56.43 100/12 33.33 0.24 Ex. 31 Q31P27 Urea 10.00 56.43 100/12 33.33 0.24 Comp. T21 P21 — 10.00 56.67 — Ex.21 33.33 Comp. T22 P22 — 10.00 56.67 — Ex. 22 33.33 Comp. T23 P23 —10.00 56.67 — Ex. 23 33.33 Comp. T24 P24 — 10.00 56.67 — Ex. 24 33.33Comp. T25 P25 — 10.00 56.67 — Ex. 25 33.33 Comp. T26 P26 — 10.00 56.67 —Ex. 26 33.33 Comp. T27 P27 — 10.00 56.67 — Ex. 27 33.33

The storage stability of the prepared coating fluids (Q21 to Q31 and T21to T27) was evaluated by the following method. The results are shown inTable II-3.

Storage Stability

Each coating fluid was left to stand still at room temperature for 1month, and then 100 cc thereof was subjected to filtration by means of anon-aqueous type polytetrafluoroethylene filter having a pore diameterof 0.45 μm and Φ×L being 18×22 mm (Chromatodisk 13N, manufactured byKurabo Industries Ltd.), whereby one which was filterable was identifiedby ◯, and one which led to clogging was identified by ×.

Each prepared coating fluid (Q21 to Q31 and T21 to T27) was applied on atriacetyl cellulose (hereinafter referred to as TAC) film (filmthickness: 80 μm, reflectance at a wavelength of 550 nm: 4.5%) subjectedto the following treatment, by means of a bar coater (No. 3) to form afilm. It was left to stand at room temperature for 30 seconds and thendried in a clean oven at 100° C. for 5 minutes, followed by curing at atemperature of 40° C. for 3 days. With respect to the obtained curedfilm, the contact angle with water, the oil-based ink wiping efficiency,the fingerprint wiping efficiency, the adhesion, the reflectance and theabrasion resistance were evaluated. The evaluation methods thereof areas follows, and the evaluation results are shown in Table II-3 and II-4.

Method for Surface Treatment of Tac Film

A coated TAC film (film thickness: 80 μm) manufactured by Nippon PaperIndustries Co., Ltd. was immersed in a 5 mass % potassium hydroxide(KOH) aqueous solution heated to 40° C. for 3 minutes to carry outalkali treatment, followed by washing with water. Then, it was immersedin a 0.5 mass % sulfuric acid (H₂SO₄) aqueous solution at roomtemperature for 30 seconds for neutralization, followed by washing withwater and drying.

Contact Angle with Water

Using an automatic contact angle meter CA-Z model, manufactured by KyowaInterface Science Co., Ltd., the contact angle when 3 μl of pure waterwas dropped, was measured.

Oil-Based Ink Wiping Efficiency

An ink applied on the surface of a cured film by means of an oil-basedink pen manufactured by Pentel Co., Ltd., was wiped off by means ofBEMCOT M-3 manufactured by Asahi Kasei Corporation, whereby the wipingefficiency was visually evaluated. A case where the ink was completelywiped off was identified by ◯, and any other cases were identified by ×.

Fingerprint Wiping Efficiency

A fingerprint was applied on the surface of a cured film and wiped offby means of BEMCOT M-3 manufactured by Asahi Kasei Corporation, wherebythe wiping efficiency was visually evaluated. A case where thefingerprint was completely wiped off was identified by ◯, and any othercases were identified by ×.

Adhesion

Each cured film on the substrate was cross-cut at 1 mm intervals to form100 sections, and an adhesive tape (Cellotape, registered trademark,manufactured by Nichiban Co., Ltd., 24 mm in width) was firmly bonded tothe cured film, and then, the adhesive tape was quickly peeled wherebypresence or absence of peeling of the cured film was visually confirmed.One having no peeling was identified by ◯, and one having peelingobserved was identified by ×.

Method for Measuring Reflectance

Using spectrophotometer UV3100PC manufactured by Shimadzu Corporation,light with a wavelength of 550 nm was permitted to enter to a cured filmat an incidence angle of 5°, whereby the reflectance was measured.

Abrasion Resistance

By means of steel wool #0000 manufactured by Nippon Steel Wool, eachcured film was rubbed 10 reciprocations under a load of 200 g/cm², andscratching on the cured film surface was visually evaluated. Theevaluation standards were as follows.

A: 0 to 5 scratch marks, B: 6 to 10 scratch marks, C: 11 to 20 scratchmarks, D: 21 or more scratch marks

Further, each prepared coating fluid (Q21 to Q31 and 21 to T27) wasapplied on a silicon wafer by spin coating to form a film. Then, it wasleft to stand for 30 seconds at room temperature, then dried in a cleanoven at 100° C. for 5 minutes and then cured at a temperature of 40° C.for 3 days to obtain a cured film having a thickness of 100 nm. Withrespect to the obtained cured film, the refractive index was evaluatedby the following method. The evaluation results are shown in Table II-4.

Method for Measuring Refractive Index

Using Ellipsometer DVA-36L manufactured by Mizojiri Optical Co., Ltd.,the refractive index was measured with light having a wavelength of 633nm.

TABLE II-3 Contact Oil-based Fingerprint Storage angle with ink wipingwiping Coating fluid stability water (°) efficiency efficiency Ex. 21Q21 ◯ >100 ◯ ◯ Ex. 22 Q22 ◯ >100 ◯ ◯ Ex. 23 Q23 ◯ >100 ◯ ◯ Ex. 24 Q24◯ >100 ◯ ◯ Ex. 25 Q25 ◯ >100 ◯ ◯ Ex. 26 Q26 ◯ >100 ◯ ◯ Ex. 27 Q27 ◯ >100◯ ◯ Ex. 28 Q28 ◯ >100 ◯ ◯ Ex. 29 Q29 ◯ >100 ◯ ◯ Ex. 30 Q30 ◯ 92 ◯ ◯ Ex.31 Q31 ◯ >100 ◯ ◯ Comp. T21 ◯ >100 ◯ ◯ Ex. 21 Comp. T22 ◯ >100 ◯ ◯ Ex.22 Comp. T23 ◯ >100 ◯ ◯ Ex. 23 Comp. T24 ◯ >100 ◯ ◯ Ex. 24 Comp. T25◯ >100 ◯ ◯ Ex. 25 Comp. T26 ◯ 92 ◯ ◯ Ex. 26 Comp. T27 ◯ >100 ◯ ◯ Ex. 27

TABLE II-4 Refractive Reflectance Abrasion Coating fluid index (%)Adhesion resistance Ex. 21 Q21 1.380 1.5 ◯ A Ex. 22 Q22 1.375 1.4 ◯ AEx. 23 Q23 1.370 1.3 ◯ A Ex. 24 Q24 1.365 1.2 ◯ A Ex. 25 Q25 1.390 1.7 ◯A Ex. 26 Q26 1.370 1.3 ◯ A Ex. 27 Q27 1.370 1.3 ◯ A Ex. 28 Q28 1.370 1.3◯ A Ex. 29 Q29 1.370 1.3 ◯ A Ex. 30 Q30 1.390 1.7 ◯ A Ex. 31 Q31 1.3801.5 ◯ A Comp. T21 1.380 1.5 ◯ C Ex. 21 Comp. T22 1.375 1.4 ◯ C Ex. 22Comp. T23 1.370 1.3 ◯ D Ex. 23 Comp. T24 1.365 1.2 ◯ D Ex. 24 Comp. T251.390 1.7 ◯ D Ex. 25 Comp. T26 1.390 1.7 ◯ C Ex. 26 Comp. T27 1.380 1.5◯ D Ex. 27

As shown in Table II-3 and II-4, in Examples 21 to 31, at a curingtemperature of 40° C., the abrasion resistance was excellent at a levelof A, and the contact angle with water was also excellent at a level ofat least 90°.

And, the storage stability of the coating fluids (Q21 to Q31) was good,and they were stable even after lo storage at room temperature for 6months.

Further, in Examples 21 to 31, characteristics of a low refractive indexof not higher than 1.4 and low reflectance are shown.

On the other hand, in Comparative Examples 21 to 27 employing coatingfluids (T21 to T27) containing no compound (B), at a curing temperatureof 40° C., the abrasion resistance was inadequate at a level of C or D.

Further, as shown in Tables II-3 and II-4, Examples 21 to 31 wereexcellent in antifouling properties such as fingerprint wipingefficiency and oil-based ink wiping efficiency, and the adhesion to thesubstrate was high.

REFERENCE EXAMPLE 21

The prepared coating fluid Q21 was applied on a TAC filter (filmthickness: 80 μm, reflectance at a wavelength of 550 nm: 4.5%) subjectedto the above-mentioned treatment, by means of a bar coater (No. 3) toform a film. It was left to stand at room temperature for 30 seconds,then dried in a clean oven at 100° C. for 5 minutes, and thereafter, noheat treatment for curing was carried out. With respect to this film,the contact angle with water, oil-based ink wiping efficiency,fingerprint wiping efficiency, adhesion, reflectance and abrasionresistance were evaluated in the same manner as in Examples 21 to 31. Asa result, the contact angle with water was larger than 100° (>100°), theoil-based ink wiping efficiency was ◯, the fingerprint wiping efficiencywas ◯, the adhesion was ◯, the reflectance was 1.5%, and the abrasionresistance was D.

INDUSTRIAL APPLICABILITY

The coating fluid for forming a film of the present invention isexcellent in storage stability and can be cured sufficiently by lowtemperature heat treatment at a level of from 40° C. to 70° C. toprovide a film excellent in abrasion resistance. Therefore, it is usefulfor e.g. a protective film for plastics, glass, ceramics, etc.

Further, the coating fluid for forming a water repellent film of thepresent invention is excellent in storage stability and can be curedsufficiently by low temperature heat treatment at a level of from 40° C.to 70° C. to provide a water repellent film having a low refractiveindex and being excellent in abrasion resistance. Therefore, it isparticularly useful for an antireflection substrate, especially as anantireflection film for display devices.

Further, the process for forming such a film is industrially useful withexcellent storage stability of the coating fluid for forming a film ofthe present invention.

The entire disclosures of Japanese Patent Application No. 2005-177434filed on Jun. 17, 2005 and Japanese Patent Application No. 2005-178016filed on Jun. 17, 2005 including specifications, claims and summariesare incorporated herein by reference in their entireties.

1. A coating fluid for forming a film, which comprises a polysiloxane(A) that consists essentially of the condensation polymerization productof a silicon compound of formula (1) as the essential component:Si(OR¹)₄  (1) wherein R¹ is a C₁₋₅ hydrocarbon group, and a compound (B)of the formula (2):

each of R², R³, R⁴ and R⁵ which are independent of one another, is ahydrogen atom or a C₁₋₅ organic group, hydroxyethyl or hydroxypropyl inan amount ranging from 0.06 to 0.20 mol of the compound of formula (B)per mol of silicon atoms of the polysiloxane (A).
 2. The coating fluidfor forming a film according to claim 1, wherein the polysiloxane (A) isa polysiloxane obtained by condensation polymerization of at least onesilicon compound of the formula (1) and at least one silicon compound ofthe formula (3):(R⁶)_(n)Si(OR⁷)_(4-n)  (3) wherein R⁶ is a hydrogen atom or a C₁₋₂₀organic group, R⁷ is a C₁₋₅ hydrocarbon group, and n is an integerranging from 1 to
 3. 3. The coating fluid for forming a film accordingto claim 2, wherein the polysiloxane (A) is a polysiloxane obtained bycondensation polymerization in a ratio ranging from 0.02 to 0.80 mol ofthe silicon compound of the formula (3) to 1 mol of the silicon compoundof the formula (1).
 4. The coating fluid for forming a film according toclaim 1, wherein the polysiloxane (A) is a polysiloxane obtained bycondensation polymerization of at least one silicon compound of theformula (1) and at least one silicon compound of the formula (4):(R^(2′))Si(OR^(3′))₃  (4) wherein R^(2′) is a fluorinated C₁₋₂₀ organicgroup, and R^(3′) is a C₁₋₅ hydrocarbon group.
 5. A water repellent filmobtained by applying the coating fluid for forming a film as defined inclaim 4 on a substrate and curing it at a temperature ranging from 40 to70° C.
 6. An anti-reflection substrate having the water repellent filmas defined in claim
 5. 7. An anti-reflection film having the waterrepellent film as defined in claim
 5. 8. The coating fluid for forming afilm according to claim 4, wherein the polysiloxane (A) is apolysiloxane obtained by condensation polymerization of at least onesilicon compound of the formula (1), at least one silicon compound ofthe formula (4) and at least one silicon compound of the formula (5)(R⁸)_(n)Si(OR⁹)_(4-n)  (5) wherein R⁸ is a hydrogen atom or a C₁₋₁₂organic group having no fluorine, R⁹ is a C₁₋₅ hydrocarbon group, and nis an integer ranging from 1 to
 3. 9. A water repellent film obtained byapplying the coating fluid for forming a film as defined in claim 8 on asubstrate and curing it at a temperature ranging from 40 to 70° C. 10.An anti-reflection substrate having the water repellent film as definedin claim
 9. 11. An anti-reflection film having the water repellent filmas defined in claim
 9. 12. The coating fluid for forming a filmaccording to claim 1, wherein the polysiloxane (A) is a polysiloxaneobtained by hydrolytic condensation polymerization of the siliconcompound of the formula (1) as the essential component.
 13. The coatingfluid for forming a film according to claim 1, wherein the polysiloxane(A) is a polysiloxane obtained by heating a mixture of a siliconcompound containing the silicon compound of the formula (1) as theessential component, a solvent and oxalic acid.
 14. A film obtained byusing the coating fluid for forming a film as defined in claim
 1. 15. Acured film obtained by applying the coating fluid for forming a film asdefined in claim 1 on a substrate and curing it at a temperature from 40to 70° C.
 16. A process for forming a film, which comprises: applyingthe coating fluid for forming a film as defined in claim 1 on asubstrate and curing it at a temperature ranging from 40 to 70° C.